Brake

About Brakes

"Brakes" refer to a set of components that work together to bring a vehicle to a stop once it is moving. Braking systems on most modern vehicles are hydraulically actuated. The brake pedal actuates a master hydraulic cylinder which, with the assistance of a vacuum-powered booster, pressurizes a hydraulic line and actuates cylinders at each wheel. A proportioning valve controls the bias of pressure to all four corners.

They cylinders at each wheel actuate either pistons in a caliper (for disc-brake applications) or a wheel-cylinder (on drum brakes). In disc brakes, the pistons push on brake pads which have friction linings. These linings are forced against brake disc-rotors, which turn with the vehicle's wheel hub. This force slows the turning of the wheel, and slows the vehicle.

Drum brakes work similarly with different components. Wheel cylinders push brake shoe-linings against the insides of a drum that spins with the wheel hub to slow the vehicle. Drums on modern cars are used in rear applications, if at all, and are mainly used for cost savings in low-demand applications, since disc brakes are much more efficient at stopping vehicles.